In high school I learned that gas for coal, wind for wind mill, and tide for water, cause a turbine to spin and that powers an electrical generator and then boom we have electricity. What I want to know is how does the generator convert the kinetic energy of the turbine into electrical energy.
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So. It has to do with how electricity and magnetism are intertwined.
To put it simply, if a magnetic field moves across wires, the magnetic field can induce a current in the wire, “pushing” the electrons along the wire.
So, in a generator, at the very simplest, you have a magnet on a shaft, that shaft is then attached to the windmill or hydroelectric turbine or the turbines in goal or gas plants, and then wrap wire around them in a big coil, you can convert the spinning energy of the turbine into electrical energy, by spinning the magnet inside the coil, which induces and electric current.
Electric motors (like those in a toy car, or a Tesla, or a fan) actually work the same exact way, but in reverse. Instead of a moving magnet inducing an electric current, you can use an electric current to make a magnet move.
If you rotate a magnet around a wire, the pull of the magnetic field tugs on the wire and creates an electric current in it. (This doesn’t violate conservation of energy, because pulling the electrons in the wire also creates drag on the movement of the magnet.) Fundamentally, a turbine is just a device that uses fluid flow as the source of the magnet’s motion in order to take advantage of this effect.
It’s just like an electric motor, except in reverse. In fact you can take an electric motor and use it to generate electricity if you find another power source to cause it to spin.
There’s all different types of electric motors, but they all involve using electricity to create a magnetic force that moves objects attached to the shaft, which causes the shaft to spin.
Most generators are AC generators, so I’ll just talk about those.
On the rotor is are electromagnets. It needs at least a north and south pole, but it’s perfectly possible to have more since that means the turbine can spin slower but produce electricity at a higher frequency. Around the rotor is the stator (the STATionary part) that has coils of wire where the electricity is created, and as the rotor spins the sequence of north and south poles passing near the coil causes a continuously changing magnetic field that has the form of a sine wave. This changing magnetic field creates a voltage in generator coils. The stator has multiple coils spaced out around the rotor. Each one is at a different point on the sine wave, so each one is at a different voltage.
When the generator is connected to a load, the voltage difference between the coils causes current to flow and power the load. This current flow creates its own magnetic field in the stator, and this new field opposes the field on the rotor that made it. This causes the rotor to slow down and is why the generator needs a source of mechanical energy to run. The windmill/turbine is overcoming the counter force* of the electricity the generator is making.
* This is the counter electromotive force (counter EMF on CEMF) other explanations may use
When you move a magnet toward a wire, the magnet repels the electrons in the wire. And the electrons in the wire do repeal the magnet in return. (You can do also the opposite)
If you spin a magnet inside a set of wires, the wires want to slow down the magnet while the magnet will push electrons in the wires. These are very small forces. But… if you wind kilometers of wire into coils (poles), put several coils kn a circle, and spin a very powerful electromagnet in the center (has a field equivalent to millions of refrigerators magnets) you can extract a lot of electricity.
Then of course, there’s quirks and tech things and so on, but basically a generator is that: A rotating magnet that induces a voltage into coils around it. An electric motor is the opposite. You can do it both ways, transform a movement into electric power or transform electric power into movement. You just need a power source, like wind water or steam or whatever, to move the generator.
Note: you can flip all things to the opposite, use both repulsion and attraction between currents and magnetic fields, you can use rotating coils and fix magnetic field. That’s just construction quirks to get some advantage in this or that usage or in this or that size.
These people have mostly explained it, when a wire feels a change in magnetic field, a current is generated in the wire. Most of the math is figuring out what change in magnetic field gets you desired current push, but one question might immediately arise, why does this not violate conservation of energy? For example if I have a magnet and drop it, that’s a changing magnetic field and if I have a wire nearby current would be generated creating electrical energy. Where did this come from, and how does the system change if I don’t have a wire to pickup the energy?
What happens is a Lorentz force is created on the magnet, so the wire actually slows down the magnet as it falls! This is a transformation of magnet’s kinetic energy into electrical energy, and without the pickup wire this force isn’t there so the object simply falls faster.
Most generators work with a rotating magnet in or near some wires, and this works essentially the same way, it gets harder to rotate the magnets if the coils are present.
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